Andre Villas-Boas fears Jan Vertonghen could miss the start of the season after suffering suspected ankle ligament damage in a pre-season friendly.

Vertonghen slipped on the sodden surface during in the opening game of the Barclays Asia Trophy in the Hong Kong Stadium.

The game was reduced to 40 minutes in each half because of the torrential rain that had fallen for several hours in Hong Kong and threatened to see the game called off.

But the game went ahead, with Vertonghen slipping and injuring his left ankle just six minutes after coming on as a half-time substitute for defender Steven Caulker. Vertonghen needed treatment for six minutes before being carried from the pitch on a stretcher.

"He might have sprained the ligaments in his left ankle," said Villas-Boas. "He will need to have an MRI scan to establish the full extent of the problem.

"But there is some range of movement, so we have to hope it won't be that long. Hopefully he'll be back for the first game of the season.

"I was concerned [about the conditions] but what can you do? It isn't great, the pitch is what it is.

"There are often problems here, but you can't change the conditions. They are extremely poor."

Match officials inspected the pitch before the scheduled kick-off, which was delayed by half-an-hour, and called both clubs to a pre-match meeting, at which it was agreed to play 40 minutes in each half.

Spurs went ahead through Gylfi Sigurdsson in the first-half, before Cabral equalised for Sunderland before half-time.

Wes Brown headed Sunderland in front, before David Karlsson added the third late on to put Paioo Di Canio's side in Saturday's final against Manchester City or South China.

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"I can't make any more comments because I made them at the press conference before this game," said Villas-Boas.